To improve operability, many electronic devices employ haptics or haptic feedback. Haptics provide information to the user of a device via the user's sense of touch. Accordingly, haptics may employ various stimuli that are sensed via touch, such as vibration, pressure, temperature, etc. Vibration (e.g., periodic motion) is commonly used to provide haptic feedback. For example, a device may momentarily vibrate when a user touches a control area of a touchscreen or when an alarm condition is triggered.
Linear resonant actuators (LRA) and eccentric rotating mass (ERM) actuators are two types haptic actuators employed to provide vibratory feedback. An ERM actuator includes an electric motor (e.g., a brushed DC motor) with an eccentric (off center) mass attached to the rotor shaft. When activated the ERM actuator produces a two-dimensional vibratory effect. An LRA includes a mass attached to a spring, and a coil proximate to the mass. Energizing the coil causes linear movement of the mass producing vibration in one dimension. Haptic systems employ driver or control circuitry coupled to a haptic actuator to induce motion in the haptic actuator.